NEW YORK, Oct 30 (Reuters) - Flooding at the second-largest refinery on the U.S. East Coast plus power glitches at two other plants and a key New Jersey terminal hub slowed the recovery in fuel supplies disrupted by Hurricane Sandy.

While the region's biggest plant, in Philadelphia, and several others were ramping up operations after escaping damage, other facilities, pipelines and terminals were struggling to restore the flow of supplies that had slowed to a trickle. Several operators cited power outages around the Linden, New Jersey, hub near the key New York harbor trading area.

Phillips 66 said there was "some flooding in low-lying areas" of its 238,000 barrel-per-day Bayway, New Jersey, plant, which was shut on Monday as a precaution. It did not say when the plant, which had lost external power, might restart.

New Jersey utility PSE&G said late in the day that it had "re-energized" three of six flooded switchyards, including equipment that can deliver power to Linden.

News of trouble at Bayway, nicknamed the "gasoline machine" for its key role in supplying motor fuel to the New York City area, turned the tide in gasoline futures which had fallen more than 2 percent as output recovered elsewhere and traders bet that fuel consumption would be hit.

By late evening, prices had reversed course to rise more than 2 percent on the New York Mercantile Exchange (NYMEX), which was due to reopen its trading floor on Wednesday. A fire at a unit of BP's Texas City refinery aided gains too.

Other power-related glitches also surfaced after the storm, which left more than 8 million customers without electricity, shut the region's seven major international airports and all but halted traffic on the nation's most heavily traveled roads.

As the storm moved north, a power outage shut Imperial Oil's 121,000-bpd Sarnia, Ontario, refinery, but the company said it expected to restart units later in the day.

Hess Corp's 70,000-bpd Port Reading, New Jersey, refinery, which had also shut ahead of Sandy, lost power and had no time frame for restarting.

The northern Line 3 segment of the Colonial Pipeline, a conduit that supplies as much as 15 percent of the East Coast's 5.2 million bpd of gasoline, diesel and fuel demand, was still idle, but the company said it had not suffered any operational damage. Portable generators were being brought in to restore power to the Linden tank farm and resume shipments.

The company asked customers to divert fuel shipments bound for the New Jersey area to southern markets.

NuStar Energy said there had been significant water damage at its Linden terminal, while Buckeye Partners LP said many of its New York, New Jersey and Connecticut facilities were also without power.

Factbox on oil operations:

The flooding at Bayway, which had been seen by experts as the refinery most vulnerable to Sandy's record 13-foot (4-meter) storm surge and subsequent power outages, is a potential second nightmare for Phillips 66, which had struggled to restore its Alliance, Louisiana, refinery after Hurricane Isaac in August. That storm pushed more than 2 feet of floodwater into the plant.

PHILLY PLANTS SEEN OK

Operations in the Philadelphia area appeared set to resume quickly. Philadelphia Energy Solutions' 330,000-bpd refinery, the biggest in the region, escaped damage and was restoring operations at the Point Breeze half of the plant that was shut, the company said, confirming a Reuters report.

Industry group Genscape said its infrared cameras detected the restart of key crude and vacuum distillation units.

Delta Air Lines subsidiary Monroe Energy's 185,000-bpd Trainer, Pennsylvania, plant operated through the storm, and was expected to reach full rates next week after a maintenance overhaul, a source with knowledge of operations said.

PBF Energy was ramping up its Delaware City refinery after minimal run-cuts, another such source said. A company spokesman confirmed reports that the plant had flared briefly, but said the incident had not affected operations.

Delaware City and PBF's 180,000-bpd Paulsboro plant in southern New Jersey, which had throttled back to reduced rates ahead of Sandy, "ran well through the storm", spokesman Michael Karlovich said.

He said personnel had completed a "thorough assessment" of the facilities, and that PBF would not provide further updates on logistics or operations.

The precautionary refinery closures were more widespread than during Hurricane Irene in August 2011, when only the Bayway plant shut completely.

John Auers, senior vice president and refining specialist at Turner, Mason & Co in Dallas, said East Coast plants, even those near the water, are better protected from potential flood damage than those that suffered weeks-long outages on the Gulf Coast following hurricanes Katrina and Rita seven years ago.

Still, even minor flooding can be a concern and plants without sufficient on-site generators may have to wait for utilities to restore outside power. The largest risk may simply lie in restarting vast, intense equipment.

"You're talking about heating up oil to fairly high temperatures, putting it through processing units at high pressure," Auers said. "Anytime you interrupt that steady-state there is always the potential for issues."

While the biggest ports remained shut, stalling delivery of some 1 million bpd of imported fuel, the Port of Boston opened without restrictions and was expected to unload a gasoline cargo later on Tuesday, an official said.

DEMAND IN FOCUS

Barring major damage, most experts expected the region's fuel supplies could bounce back quickly, while demand was likely to take a much deeper knock. Some 170,000 bpd of jet fuel demand alone was shut for a third day as all three major New York area airports remained shut, with no date for resuming flights.

Benchmark New York gasoline futures prices, which rallied more than 6 percent before the storm as traders feared a disruption in supplies, closed 1 percent lower. U.S. crude oil futures rose slightly, reversing Monday's dip.

One trader offering to sell physical cargoes in the New York Harbor market found no buyers on Monday.

"For the moment you have a big black hole where there used to be oil demand," said Credit Suisse oil analyst Jan Stuart. He said 80 percent of demand in the New York metropolitan area had been affected somehow.

"In the end, the demand deficit outweighs the supply deficit."

Airlines had canceled more than 15,770 flights in the past four days, flight-tracking service FlightAware said.

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